1. Field of the Invention
The present invention relates to the microbiological industry, and specifically to a method for producing an L-amino acid using a bacterium of the Enterobacteriaceae family which has been modified to attenuate expression of the sfmACDFH-fimZ cluster or the fimZ gene.
2. Brief Description of the Related Art
Conventionally, L-amino acids are industrially produced by fermentation methods utilizing strains of microorganisms obtained from natural sources, or mutants thereof. Typically, the microorganisms are modified to enhance production yields of L-amino acids.
Many techniques to enhance L-amino acid production yields have been reported, including transformation of microorganisms with recombinant DNA (see, for example, U.S. Pat. No. 4,278,765). Other techniques for enhancing production yields include increasing the activities of enzymes involved in amino acid biosynthesis and/or desensitizing the target enzymes of the feedback inhibition by the resulting L-amino acid (see, for example, WO 95/16042 or U.S. Pat. Nos. 4,346,170; 5,661,012 and 6,040,160).
Another way to enhance L-amino acid production yields is to attenuate expression of a gene or several genes encoding protein(s) involved in the degradation of the target L-amino acid, the diversion of the precursors of the target L-amino acid from the L-amino acid biosynthetic pathway, and the redistribution of carbon, nitrogen, and phosphate fluxes, and genes encoding toxins etc.
The sfmA gene encodes the SfmA protein, which is a putative fimbrial-like protein. The sfmc gene encodes the SfmC protein, which is a putative shaperone. The sfmD gene encodes the SfmD protein, which is a putative outer membrane protein. The sfmH gene encodes the SfmH protein, which is a putative protein involved fimbrial assembly. The sfmF gene encodes the SfmF protein, which is a putative fimbrial-like protein. The fimZ gene encodes the FimZ protein, which is a putative transcriptional regulator (http://ecocyc.org).
But currently, there have been no reports of attenuating expression of the sfmACDFH-fimZ cluster or the fimZ gene for the purpose of producing L-amino acids.